Please make sure to review the OSC zoning requirements for green spaces, etc. The calculation is determined by your total building acreage, which is your total acreage, minus any greenspace requirements, minus your roads that you design in your site plan. Be sure to understand what the municipality will count as green space, and what they do not count as green space, as you may have some other areas that you design on your site plan that take away from your total buildable acreage. After you have your total buildable acreage, then you apply the density calculation from the required zoning.